World modelling goes global

Staff at the Systems Analysis Research Unit of the UK Departments of the Environment and Transport, led by P.C. Roberts, have built a model of the world economic system and its natural resources. In September 1976, the modelling work of SARU was presented to a symposium at the International Institute for Applied Systems Analysis (IIASA) in Austria. SARU's work on world modelling has so far received little exposure in the UK. Accordingly, the British National Committee for IIASA arranged for a one-day public presentation of SARU's modelling work at the Royal Society, London, on 3 October 1977.     

Basic health care in El Salvador

Health care in a conventional war has its own characteristics. Health care in a guerilla war, as exists at present in El Salvador, adds to this some new aspects.     

Book reviews

Frances Sharples is a terrestrial ecologist in the Environmental Science Division of the Oak Ridge National Laboratory in Oak Ridge, Tennessee, operated by Martin Marietta Energy Systems, Inc., under Contract No. DE-AC05-840R21400 with the US Department of Energy. Publication No. 3413, Environmental Sciences Division, ORNL.     

Quantitative Determination of Formaldehyde in the Parts Per Hundred Million Concentration Level

A new method has been developed for the determination of trace quantities of formaldehyde and appears to be superior to existing methods. The procedure is based on a modification of Schiff’s test for aldehydes. A mixture of dichlorosulfitomercurate II complex and acid bleached pararosaniline hydrochloride is used as the reagent. In the presence of formaldehyde, a purple color is produced. The method is highly sensitive to formaldehyde and acetaldehyde, simple and does not require concentrated acids. When applied to air pollution studies, the method is virtually free of interferences from higher aldehydes. The paper describes the application of this method to spot sampling of the atmosphere and to continuous atmospheric analysis.     

A retro-synthesis approach for hazard evaluation and risk screening

Risk screening instruments can be very useful for evaluating hazards and establishing priorities for risk reduction. Further, these instruments can provide educational value to field staff when they are distributed to individuals outside of traditional process safety roles. This paper describes a retro-synthesis technique whereby risk screening instruments can be readily generated for these types of hazard evaluation and priority setting activities. Further, by utilizing a retro-synthesis approach, data gathered at the field level can often be drawn upon at a later point if a more detailed risk assessment is required. The retro-synthesis approach involves working backwards from traditional risk functions (relationships) so as to define the predominant elements for incorporation within the risk screening instrument. Compared to conventional techniques, the retro-synthesis approach utilizes deductive reasoning techniques in a manner similar to Fault Tree Analysis (FTA). However, the directional relationships that are established between causes and consequences become inverted.For example, risk can be defined as a function of “likelihood” and “severity”, where “severity” may be a function of the “energy released” and the “exposure group”. Similarly, the “energy released” is often a function of the “properties of the material involved” and the “amount of material released”. Through identifying these relationships, “risk” in this example can be characterized as a function of “likelihood”, “exposure group”, “properties of the material involved”, and “amount of material released”. Further, by highlighting the various influential parameters, the relationships between each of these parameters, as related to risk, can also be understood. Once the various terms and functions are defined, screening categories can then be developed to quantify each of the terms so as to allow for an approximation of the relative risk involved for the given scenarios.This approach benefits from being simple to develop, maintaining alignment with the mathematics required for more detailed quantitative risk assessments, and generating screening categories which can be given to field staff. Through careful construction of the screening categories field staff can then rapidly, and in a reproducible manner, screen a large number of scenarios so as to identify those situations which represent priority hazards.     

Entwicklung der Ökotoxikologie von Pflanzenschutzmitteln in den letzten 25 Jahren: Von ersten Diskussionen über Prüforganismen zur probabilistischen Risikoanalyse

In Europe as well as in Germany a remarkable development within the last 25 years took place in the assessment of ecotoxicological effects of Plant Protection Products (PPPs). The starting point was a comparative, retrospective toxicity testing of some selected indicator species. Then, first attempts of a quantitative, prospective hazard and risk assessment with relevant exposure evaluations were made. Currently a probabilistic risk analysis on the landscape level is discussed.Based on personal experiences within the last decades this contribution will highlight the different developments of the ecotoxicological evaluation of PPPs. At first, the selection of suitable test species and the development of suitable standardized test methods was the main task. Thereafter, the discussions focused more on long-term, chronic effects instead of solely acute ones, the development of focused higher tier studies adjusted to better address the specific properties of a PPP and/or the specific concerns resulting from its application, as well as multi-species and ecosystem approaches. With the availability of suitable computer based models a more precise exposure calculation was possible, which allows a more realistic exposure assessment instead of simple worstcase assumptions. Current discussions focus on probabilistic exposure assessments at a local scale.All these developments took place regardless of the insufficient (political) definition of the protection goal and — as a consequence — the need and extent of appropriate safety factors. The development of ecotoxicology was mostly driven by political trends in Europe, mainly by the harmonized registration of PPPs under the still valid Annexes II and III (1996) of the EU Directive 91/414 and the thereby initiated further progression. In the context of this development more and more scientists were offered interesting job opportunities.     

Pesticide modelling for a small catchment using SWAT-2000

Pesticides in stream flow from the 142 ha Colworth catchment in Bedfordshire, UK were monitored from October 1999 to December 2000. About 47% of the catchment is tile-drained and different pesticides and cropping patterns have recently been evaluated in terms of their effect on nutrient and pesticide losses to the stream. The data from Colworth were used to test soil and water assessment tool (SWAT) 2000 predictions of pesticide concentrations at the catchment outlet. A sound model set-up to carry out pesticide modelling was created by means of hydrological modelling with proper simulation of crop growth and evapotranspiration. The pesticides terbuthylazine, terbutryn, cyanazine and bentazone were modelled. There was close agreement between SWAT-predicted pesticide concentration values and observations. Scenario trials were conducted to explore management options for reducing pesticide loads arriving at the catchment outlet. The results obtained indicate that SWAT can be used as a tool to understand pesticide behavior at the catchment scale.     

Reservoir sedimentation and environmental degradation: assessing trends in sediment-associated trace elements in Grenada Lake, Mississippi

Sediments impounded within flood control reservoirs are potentially important archives of environmental and geomorphic processes occurring within drainage basins. The concentrations of select sediment-associated trace elements were assessed within the impoundment of Grenada Lake, a relatively large flood control reservoir in Mississippi with a history of contaminant bioaccumulation in fish. The post-construction sediments (after 1954) are discriminated from the pre-construction sediments (before 1954) based on depth variations in sediment texture and 137Cs emissions. The concentrations of select trace elements of the post-1954 sediments all are statistically greater than the pre-1954 sediments, and these same sediments also are enriched in clay. Once these concentrations are normalized by clay content, all trace elements in the post-1954 sediments are lower in concentration than the pre-1954 normalized sediments. Moreover, the trace elements when normalized by clay or Al content show virtually no change vertically (over time) within the reservoir impoundment. This suggests that the sources of these sediment-associated trace elements within Grenada Lake, whether natural or anthropogenic, have not changed appreciably over the lifespan of the reservoir and that the degradation of sedimentologic and ecologic indices within the lake are due to the sequestration of clay or clay-sized materials.     

The critical re-action: Learning from accidents

How do organizations react and learn from accidents? The current paper deals with the justified necessity of acting upon, and learning from accidents. The aim is to discuss organizational dynamics and interplay, evoked and put into (re)action ‘after the fact’.The paper is part of an interview study that was designed to invite individuals to reflect back, and search for patterns in terms of how they interpret the learning impact of an accident, not just in terms of changes within their own organization that can be traced back to accidents, but for the sector as a whole. A presumption for this study was the importance to look at organizational interaction, i.e. how organizations act, affect, and speak with each other. In all 30 people from the rail and marine sector were interviewed with regard to (1) revealed changes in the aftermath of the accident, and (2) conditions for learning from accidents. Thematically, the interviews had two major accidents in Norway as a background theme: The high-speed craft MS Sleipner-accident (1999) and the railway accident at Åsta (2000).The paper reports and discusses key findings from the study, with a specific focus on the interplay between actors and parallel processes in the aftermaths of an accident.